Sometimes, when a subject vehicle is running, cargoes suddenly fall off a loading platform of a preceding cargo vehicle toward the front of the subject vehicle. In this case, the driver starts to monitor the falling cargoes (hereinafter, referred to as falling objects). Then, the driver takes a measure after determining that the falling objects will endanger the driver. Therefore, the driver may not be able to avoid the falling objects.
Also, the falling objects may exert an influence even on vehicles (hereinafter, referred to as oncoming vehicles) running in lanes opposite to the lane where the cargo vehicle runs. Especially, in a curve, if cargoes fall off the cargo vehicle toward the opposite lanes, it is very difficult for oncoming vehicles to avoid the cargoes.
Also, in a case where a saddle-ridden type vehicle is running between the subject vehicle and the cargo vehicle, the falling objects may cause the saddle-ridden type vehicle to fall down. For this reason, the driver of the subject vehicle needs to monitor both of the falling objects and the saddle-ridden type vehicle and take a measure. Therefore, the burden on the driver is large.
In the related art, it has been proposed a device which repeatedly acquires an image of the view in front of a subject vehicle equipped with the device, compares a plurality of consecutive images acquired in chronological order, sets a first horizontal line “A”, for example, with reference to the loading platform of a preceding vehicle in the plurality of images, sets a horizontal line “B” below the horizontal line “A”, detects that an object has crossed each of the horizontal lines “A” and “B”, calculates the speed at which the object moves downward, on the basis of the distance between the horizontal lines “A” and “B” and the image acquisition interval, quantifies the possibility that the object is a falling object, and warns a driver if the possibility is larger than a threshold (see Patent Document 1 for instance).
Patent Document 1: Japanese Patent Application Publication No. 2010-108371A
Therefore, it is possible to reduce the risk of missing a falling object according to the technology disclosed in Patent Document 1. However, in Patent Document 1, since a falling object is detected if the falling object crosses the horizontal line “A” set with reference to the loading platform, the driver starts to monitor the falling object after falling of the object occurs and takes a measure after determining that the falling object will endanger the driver. Consequently, similarly in the related art, if cargoes suddenly fall off, the driver may not be able to avoid the falling cargoes.
Also, Patent Document 1 does not mention about the point that the falling objects may exert the oncoming vehicles and the point that there is a risk that saddle-ridden type vehicles running in front of the subject vehicle equipped with the device may fall down.